1. Department of Molecular Biology, University of Bergen, N-5020 Bergen, Norway
2. Department of Surgical Sciences, University of Bergen and Haukeland University Hospital, N-5021 Bergen, Norway
3. Institute of Molecular Biology, University of Oregon, Eugene, OR 97403-1229, U.S.A.
4. INSERM U496, Centre G. Hayem, Hopital Saint-Louis, 1, Avenue Claude Vellefaux, 75010 Paris, France